1. Field of the Invention
The present invention relates to a system for supplying current through the ground for an electric vehicle, particularly for an electric rail vehicle.
It also relates to an electric vehicle supplied by means of such a system.
2. History of the Related Art
The expression xe2x80x9csystem for supplying current through the groundxe2x80x9d should be understood to mean a supply system by means of which the electrical energy needed to supply the motor of the vehicle is delivered via a segmented conducting track with which the roadway on which the vehicle runs is equipped, the energized segments of which conducting track are at any moment covered by the outline of the vehicle, as opposed to supply systems using a network of overhead. lines against which a current pick-up pantograph is applied.
Supply systems using overhead lines have a number of unacceptable drawbacks, especially drawbacks relating to aesthetic appearance, which make them unsuitable for supplying a vehicle intended to run through protected historical areas, for example classified urban centres.
Systems for supplying current through the ground, in which the supply devices for the conducting tracks are incorporated into the roadway, overcome this drawback.
At the present time, there are several types of systems for supplying current through the ground.
One example of a known system is described in document EP-A-0,761,493. This system comprises a conducting track consisting of a succession of plates, electrically insolated from each other, which cover a duct within which an elastically deformable ribbon containing a ferromagnetic material extends, the two faces of which ribbon are covered with a conductive material.
The upper face of the ribbon is connected to a supply line.
According to this technique, the rail vehicle is equipped with magnets suitable for magnetically attracting the ribbon so that the latter comes into contact via its upper face with one of the plates of the conducting track against which a supply collector shoe on the vehicle moves.
This type of supply system, although aesthetically more attractive, has a not insignificant response time and requires the provision of a moving element, namely the elastically deformable ribbon, which is liable to cause a not insignificant number of malfunctions.
The object of the invention is to remedy. these drawbacks and to provide a system for supplying current through the ground having great operating simplicity, having a minimal response time and making it possible to achieve greater safety, reliability and availability.
The subject of the invention is therefore a system for supplying current through the ground for an electric vehicle, especially for a rail vehicle, comprising a succession of conducting segments which are electrically isolated from each other and together form a conducting supply track against which at least one supply collector shoe on the vehicle is applied, this or these collector shoes coming successively into contact with the segments during the movement of the vehicle, and a set of high-voltage supply devices each connected to a conducting segment and each provided with means for detecting a collector shoe and with switching means suitable for selectively causing a corresponding segment to be supplied with current when a collector shoe is present on the latter and causing the said segment to be connected to a zero-potential source when a collector shoe is not present thereon, characterized in that the switching means include a pair of elements forming static switches controlled by the detection means in order to cause the corresponding segment to be supplied with current when a collector shoe is present thereon and to be connected to the zero-potential source when a collector shoe is not present thereon respectively, and in that each supply device furthermore includes short-circuiting means which are forced into the closed state, and are interposed between the corresponding segment and the zero-potential source, and which are made to open by the detection means.
This system for supplying current through the ground may furthermore include one or more of the following characteristics, taken in isolation or in any technically possible combination:
the means for detecting when a collector shoe is present on the corresponding segment include means for detecting a coded signal transmitted, by conduction and by carrier current, by the vehicle to the said device via the collector shoe;
since the coded signal carries coded information relating to the vehicle which has transmitted it, the detection means include means for processing the said information and means for comparing data resulting from the said processing with data corresponding to information relating to the vehicle permitted to run on the conducting track;
the detection means include means for checking that the coded signal has been received in its entirety, by processing a redundant cyclic code incorporated into the said signal;
it furthermore includes a device for monitoring the voltage on each segment connected to each of the said detection means, the said monitoring devices comprising means for comparing the voltage on the corresponding segment with a maximum threshold value, and a set of logic circuits designed to cause the short-circuiting means to close should the threshold value be exceeded and a collector shoe not be present;
the monitoring device constitutes an element independent of the processing means;
each supply device is provided with a fuse placed in series on the switch-forming element that controls the supply of current to the corresponding segment;
the detection means are connected to the devices for supplying current to a predetermined number of immediately adjacent segments in order to position the switching means of these devices so as to supply the respective segments with current when the said detection means operate the switching means in such a way as to cause the segment that corresponds to them to be supplied with current;
the detection means include a microprocessor connected to an amplifier and to a passband filter, the output of which controls the power and/or control switching of the switch-forming elements;
the elements forming static switches consist of insulated-gate bipolar transistors (IGBTs);
each supply device includes means for monitoring the voltage across the terminals of the IGBT transistors for the purpose of preventing the corresponding segment from being supplied with current in the presence of a malfunction, especially in the presence of a current flowing through the transistors having a value greater than a permissible maximum value;
the supply devices are each disposed in a removable module placed in a duct which is made in a roadway along which the vehicle runs and is covered in a sealed manner by the conducting segments, a highvoltage supply line and a line set at a zero potential providing a supply return being disposed longitudinally in the duct;
the duct is disposed approximately in the central part of the area of the roadway along which the vehicle runs;
the means for supplying current to the switching means and to the detection means comprise the high-voltage supply line;
when the vehicle has a second collector shoe providing a return for the supply current, the detection means include means for discriminating between the polarity of the supply and current-return collector shoes;
the outputs of the supply devices constitute a means for locating the vehicle, intended to locally operate signalling devices, and/or a means for detecting malfunctions for the purpose of carrying out a diagnostic check.
The subject of the invention is also an electric vehicle intended to be supplied by means of a system for supplying current through the ground, as defined above, characterized in that it includes at least one collector shoe for supplying current to the motor of the vehicle, which collector shoe is intended to be applied against the conducting track of the system for supplying current through the ground and to which collector shoe are connected means for transmitting a coded signal conveying information relating to the type of vehicle to which the electric vehicle belongs.
Preferably, when the vehicle consists of an electric vehicle guided by a guide rail, the return of the supply current is provided by rails along which the rail vehicle runs or by the guide rail.
As a variant, the vehicle includes at least one second collector shoe providing the return of the supply current, this second collector shoe being longitudinally offset with respect to the shoe for supplying current to a predetermined number of segments.